1. Field of the Invention
The present invention relates to a photosensor device for photoelectric conversion, and more particularly to a photosensor device for photoelectric conversion adapted for use for example in a long image sensor.
2. Related Background Art
Conventional photosensor devices, such as CCD, have been prepared by diffusion processes on a semiconductor substrate. Therefore the size thereof is limited, at maximum, to the size of the semiconductor substrate, and it has been difficult to obtain a long sensor array. Also in the case of forming the photosensor device on another substrate, as a system, there is required a process of adhering a separately prepared semiconductor sensor chip on the substrate, thus requiring a number of steps and resulting in a lowered accuracy of registration.
On the other hand, for obtaining wider freedom of selection of the substrate, there has been developed a photosensor device utilizing amorphous silicon. However, transistors based on amorphous silicon have been inevitably slow response time.
In order to overcome this drawback, there has been proposed, in the Japanese Laid-open Patent No. 59-126666, a method of forming a sensor portion with amorphous silicon and a transistor portion with polycrystalline silicon. However this method requires an increased number of steps and involves a high cost, since the photosensor based on amorphous silicon is prepared after the polycrystalline silicon transistor is prepared by an ordinary IC process.
In this manner it has been difficult to produce the photosensor device of satisfactory performance and low cost on a non-semiconductor substrate.